Presently available excavating equipment permits digging rapidly so that excavation work can be done and the excavation immediately filled. However, installations which require personnel to enter into the excavation (which can be rather deep and through unstable soil) have the potential for cave-ins. Such cave-ins of the excavation not only interfere with the maintenance or construction operations, but also may cause serious injury or even loss of life to working personnel. There are various types of devices at this time in the field which are utilized in these maintenance and construction trenches or excavation shoring operations to support be placed against the walls of the excavation. Samples of shoring devices generally known in the field include shoring shields, skeleton boxes, walers, vertical shores, and four-way manhole braces.
The various types of shoring devices generally incorporate hydraulic cylinder arrangements which are used for shoring the sides of trenches or excavations. It is common for devices such as these to utilize one or more horizontally disposed vertically spaced hydraulic cylinder/piston units that are connected at their opposite ends to shoring rails which extend vertically and which will be held against the opposite sides of the trench when the hydraulic cylinder/piston units are expanded. Another common shoring device uses one or more horizontally disposed, horizontally spaced, hydraulic cylinder and piston units connected pivotally at their opposite ends to horizontal shoring rails which butt against the excavation walls, shoring timbers or sheeting which may be vertically disposed at the opposite sides of the trench. Each of these types of shoring devices operate so that the cylinder and piston units act as cross-braces extending across the trench. Once the shoring devices are inserted into the trench, hydraulic fluid is pumped into the cylinders to force the pistons to extend and thereby to jack the shoring rails apart to the desired extent, and thereby hold the shoring rails or shoring boards tightly against the opposite walls of the trench to prevent sloughing of the material behind the boards or to prevent such dangers as cave-ins. Often, oversleeves are placed so as to surround and cover the piston to protect it from dirt and the like. The oversleeve slides over the cylinder when the hydraulic piston is retracted and extends with the piston exposing the cylinder.
Currently, there exists various types of hydraulic jacking units which are provided with assorted positive supporting mechanisms to lock the jack into extended position and to fix the relative position of the piston and cylinder units so as to prevent retraction of the piston into the cylinder even in the event of pressure loss or release from the cylinder. Such devices generally utilize either a pin, as disclosed in U.S. Pat. No. 4,682,914 to Aihara; 3,224,201 to Brunton; 3,851,856 to Berg; and U.K. Patent No. 2,095,719, or a threaded piston with a locking screw, as disclosed in U.S. Pat. No. 3,905,279 to Yadon; 4,787,781 to Bradberry; 3,766,740 to Teegan; 4,449,734 to Cory; 3,321,182 to Elenberg; 4,247,082 to Sjolund and Japanese Patent No. 1,459,090.
Unfortunately, the above referenced devices generally fail to provide for rapid and simple operator activation positioning and engagement during set up, operation, and breakdown of the shoring device and additionally fail to provide for the flexibility of linear locking. Further, the prior art devices often allow for exposed threads, where threads are used, as part of the positioning or locking mechanism utilized with the shoring device, such threads being easily damaged and clogged with dirt, concrete or other foreign matter which is often utilized in conjunction with trenching operations. Still further, these devices can be properly locked only after the device is in the trench, whereas the present invention provides the alternative of linear locking prior to placing the shoring device or hydraulic cylinder into a trench or other end use location.
Accordingly, the quick-release cam lock of the present invention provides a means for quickly and easily locking a hydraulic cylinder/piston arrangement at any desired width by means of a positive locking cam mechanism while also providing for a quick-release mechanism for ease of operability during repositioning of the hydraulic cylinder/piston arrangement. Notwithstanding the various devices referred to above, various other problems associated with devices for preventing the retraction of the piston into the cylinder, even in the event of pressure loss or release from the cylinder, are solved in the new and improved quick-release cam lock for hydraulic cylinders of the present invention.